A plethora of applications exist for effecting electrical contact between two conductors. One significant application is effecting interconnection between the leads of an integrated circuit device and conductive pads or terminals on a printed circuit board which serves to effect an interfacing between the integrated circuit device and a tester apparatus. Such apparatus serve to evaluate performance of integrated circuit devices.
Numerous considerations bear upon the structure employed to interconnect the IC and the printed circuit board. These factors both include electrical and mechanical considerations. One prior art structure which seeks to accomplish the purpose of the present invention is known as the Yamaichi contact. This type of contact includes an inverted L-shaped support having a cantilevered contacting portion mounted at the distal end of the generally horizontal leg of the inverted, L-shaped support, and extending generally parallel to that leg. The distal end of the contacting portion is upwardly turned so that a point thereof is engageable by a lead of an integrated circuit device to be contacted. The support, in turn, is engaged in some manner with or through a pad or terminal portion of a printed circuit board.
One of the mechanical considerations to be taken into account in designing an interconnect system is that a wiping action should be accomplished between the contact itself and the lead of the IC by which the contact is engaged. The wiping action functions to effect maximization of effective contact in view of oxide build-up which can occur. In effect, the wiping action enables a good interface to be accomplished between the contact and the lead of the IC.
In view of the fact that the cantilevered portion of the Yamaichi contact has some measure of flexibility, a wiping action can be accomplished. Another mechanical consideration that must be taken into account, however, is the desire to deter bending of a lead on the IC. The Yamaichi contact does not fully accomplish this goal.
Finally with respect to mechanical considerations, it is desirable that wiping action can be accomplished at the interface between the second end of the contact and the printed circuit board. In view of the construction of the Yamaichi contact, it is precluded from allowing such wiping action at the lower end of the contact.
Further, the Yamichi device does not sufficiently consider the electrical dictates for an interconnecting contact system. An interconnecting contact should be a high speed, short path device. Derivatively, such a contact should have a low inductance without having a controlled impedance requirement. Because of the construction of the Yamaichi contact, it does not adequately satisfy these requirements.
U.S. Pat. No. 4,445,735 which issued on May 1, 1984 illustrates another type of electrical connection device. The device of that patent serves to establish an electrical connection between contacts of a circuit network on a substrate and contact pads of a conductor network on a printed circuit board. This device is an improvement over the Yamaichi contact in that it is higher in speed and lower in inductance than the Yamaichi device. It has elastomeric means for mounting one or more contacts in a housing. The elastomeric biasing and mounting enables wiping action to be effected at both upper and lower ends of the contact. That is, both the end which engages an IC lead and the end which engages a printed circuit board contact pad can be wiped across the surfaces intended to be contacted.
The device of the '735 patent, however, retains some limitations. While some wiping action is afforded at both upper and lower ends of the contact, the amount of such wiping action is relative limited because of the elastomeric elements being used generally for effecting biasing rather than free floating suspension of the contacts. As a result of the mounting means incorporated in the '735 patent, there will be a primary tendency for some retraction of the contact point in a generally vertical direction, but there will be only a small component of lateral movement to effect wiping. Additionally, because of the lack of any significant free floating effect, lead bending on an integrated circuit being tested can occur.
It is to these dictates and shortcomings of the prior art that the present invention is directed. It is an improved electrical interconnecting system which addresses the dictates of the prior art and resolves problems thereof.